I would like to use a upstart user session to run some jobs under user control. My machine has mythbuntu installed which means I have lightdm which starts an xfce4-session. How should I replace my current configuration to have my xfce4-session running under init --user?

At the moment my /usr/share/xsessions/mythbuntu.desktop runs /usr/share/mythbuntu/session.sh which does exec startxfce4 which runs /etc/xdg/xfce4/xinitrc which in turn runs xfce4-session. I'm not sure into which part of this chain to execute init --user and then how to resume the chain. Do I need to create a user job that executes whatever I replaced with init --user?